Sufficient grip force and appropriate grasp speed provided by a prosthetic hand are essential for daily use. However, due to limitations in size and weight, it is very challenging to select motors that can generate enough power to provide sufficient grip force and high grasp speed. Accordingly, this research proposes a new prosthetic hand design using a dual-motor actuator as an actuation strategy, which consists of two motors separated by a differential mechanism to operate at the load (high force) and no-load (high speed) conditions individually. One motor is used for creating a high torque and the other for creating a high speed, so the prosthetic hand can operate at the loads without using a high-power motor with excessive size and weight. The developed prosthetic hand can perform grasping motions with the following achievements: It can provide a maximum grip force of 80.2 N and maintain a maximum of 62 N with non-backdrivable mechanisms, and provide an average closing time of 1.2 s. Furthermore, the design can provide more grip force than research prosthetic hands using a single motor.